Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, a generator, a gearbox, a nacelle, and a rotor. The rotor typically includes a rotatable hub having one or more rotor blades attached thereto. A pitch bearing is typically configured operably between the hub and a blade root of the rotor blade to allow for rotation about a pitch axis. The rotor blades capture kinetic energy of wind using known airfoil principles. The rotor blades transmit the kinetic energy in the form of rotational energy so as to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid.
It is known that the operation of a wind turbine depends on the wind speed. For example, wind turbines have predetermined wind speed threshold values for determining the operational condition of the wind energy system. One such threshold value is the cut-in wind speed which is defined as the wind speed where the wind energy system starts to generate power. Another example is the cut-out speed which is defined as the highest wind speed during which the wind turbine may be operated while delivering power. Normally, generating energy is stopped at wind speeds higher than the cut-out speed.
Conventional systems and methods for starting the wind turbine uses a predetermined, fixed cut-in wind speed that is typically based on product and/or wind turbine configuration. Actual wind conditions, however, may vary from the estimated wind conditions used to determine the cut-in wind speed. In addition, the wind speed often fluctuates around the cut-in wind speed. As such, the wind turbine may start up, but will not run continuously due to insufficient wind speed and therefore shuts down. Accordingly, the wind turbine repeatedly starts up and shuts down during low wind speed conditions, thereby resulting in a loss of energy production in low wind bins and a reduction in wind turbine power efficiency.
Accordingly, an improved system and method for operating a wind turbine during low wind-speed conditions would be welcomed in the technology. More specifically, a system and method that continuously adjusted the cut-in wind speed of the wind turbine would be advantageous.